1. Field of the Invention
The present invention relates to a display device and method of fabrication thereof and, more particularly, to an Organic Light-Emitting Display (OLED) and method of fabrication thereof.
2. Description of the Related Art
An OLED is provided with N×M sub-pixels arranged in a matrix configuration, and is classified as a passive matrix LED or an active matrix LED depending upon the manner of driving the N×M sub-pixels.
Each pixel of the active matrix OLED includes a pixel electrode and at least one Thin Film Transistor (TFT) for supplying an electrical signal to the pixel electrode. Furthermore, the active matrix OLED can include a pixel portion and a circuit portion on a single substrate. In the pixel portion, the pixel is arranged in a matrix configuration. The circuit portion has a circuit for controlling the pixel portion. The circuit portion is arranged at a periphery of the pixel portion, and the circuit for controlling the pixel portion includes TFTs. Consequently, the active matrix OLED can include respective TFTs in the pixel portion and the circuit portion, i.e., a pixel TFT and a circuit TFT.
A TFT has been discussed in Japanese Laid-Open Patent Publication No. H05-55582. The TFT discussed in the Japanese Patent includes a first blocking layer formed of silicon nitride arranged on an insulating substrate, an insulating layer formed of silicon oxide arranged on the first blocking layer, a semiconductor layer arranged on the insulating layer, a gate electrode arranged on the semiconductor layer, a second blocking layer formed of silicon nitride arranged on the gate electrode, and an interlayer insulating layer formed of PSG arranged on the second blocking layer. However, commonly applying this TFT to the circuit TFT and the pixel TFT can prevent optimization of electrical properties of the circuit TFT and the pixel TFT requiring different electrical properties.